1. Technical Field of the Invention
The present invention relates to a processing apparatus for applying a designated treatment on substrates to be processed, for example, semiconductor wafers, LCD (liquid crystal display) glass substrates, or the like.
2. Description of the Related Art
Generally, in the manufacturing process for semiconductor devices, a cleaning systems is employed in order to remove various contamination adhering to surfaces of the semiconductor wafers, for example, particles, organic contaminants, metal impurities, or the like. A single wafer processing system on behalf of the cleaning system is generally provided with a spin cleaning apparatus.
As an example, there is known a processing apparatus equipped with a scrubber, disclosed in Japanese Unexamined Patent Publication No. 8-243518. A scrubbing in this field means scouring off particles etc. from to the surfaces of the wafers by contacting a rotational processing member having a member, such as brush or sponge, with the surfaces of the wafers while rotating the unit. This conventional processing apparatus includes an elevating and rotating arm provided, at a tip thereof, with a power source in various forms, i.e. air cylinder, actuator, etc. Arranged below such a power source is an elevating and rotating shaft having its lower end to which cleaning gear, i.e. the processing member is attached.
When the power source is activated to apply up-and down thrust on the shaft, then the thrust acts on the processing member, so that it does press the surface of the wafer. The total amount of the thrust acting on the processing member and its weight is equivalent to contact pressure (i.e. pressure per unit area) applied on the wafer by the processing member. In order to clean the surfaces of the wafers favorably, it is important to control the contact pressure within a designated range and rotate the processing member at predetermined revolutions.
In the conventional processing apparatus, a rotating mechanism for rotating the processing member comprises a motor arranged in a position apart from the shaft, for example a base part of an arm member, a driving pulley rotatably secured to the motor, a driven pulley secured on the vicinity of a top of the shaft and a belt wound on both driving pulley and driven pulley. On rotation of the motor, the rotation is transmitted from the belt to the shaft, so that the processing member does revolve.
In the conventional processing apparatus, however, an establishment space for setting a rotating mechanism carrying such power-transmitting components as the belt, the pulleys, etc. extends from the tip of the arm member to the base part. Therefore, the apparatus has problems that the arm is large-sized and the interior structure of the arm is complicated. Additionally, the belt's rotation over the driving pulley and the driven pulley causes the belt and both pulleys to be rubbed to make dust. If the dust diffuses around, it may cause the sticking of particles onto the wafers, so that the efficiency of cleaning may be reduced.
Furthermore, in the conventional processing apparatus, there is a high probability that tension of the belt is exerted on the shaft through the driven pulley thereby to exert a bad influence on the elevation and rotation of the shaft. Additionally, depending on the circumstances, it happens that the transmission loss is caused due to the belt's loosing. Accordingly, there is a case that the shaft insecurely operates during the cleaning process and therefore, it is not always easy to control both contact pressure and rotation of the processing member.